Manually changing forwards on server

I have recently had the need to change all of my "forwarding to" addresses that I had previously set up in cpanel's "Forwarding Maintenance" feature under the "email" section.

I logged into my server and went to etc/valiases/mydomain and copied the file to my desktop. Then I used notepad to mass change all of my forward to addresses. I copied
the file back to my server and all of the changes showed up in cpanel + the new forwards worked.

However, If I now want to add a new forward via cpanel, it gives me the following message:
Fatal! Write Failure: /etc/valiases/mydomain. Ignore any messages of success this can only result in failure!

and the new forward does not show up in the master list.

I looked at the write permissions for the other files and they were all 644, so I re-cmoded
my domain's file to that, but that still didn't work.

I also restarted BIND, Apache, Exim & pop3 server in my WHM, but that also didn't change anything.

Does anyone know of another file that also may need to be changed in order for this to work again? Or should I just delete the file and manually re-enter all of my forwards through cpanel again (not my first option, but will do if the only way to get this fixed again)?